Method of forming encapsulation structure for organic light-emitting device

ABSTRACT

A method of forming an encapsulation structure for an organic light-emitting device is disclosed. The method is applied to organic light-emitting devices (OLED) and performed in a single reaction chamber. The method includes steps of placing an organic light-emitting device into a plasma chamber, forming a first buffer layer on the organic light-emitting device, forming a first passivation layer on the first buffer layer, forming a second buffer layer on the first passivation layer, and forming a second passivation layer on the second buffer layer.

FIELD OF THE INVENTION

[0001] This invention relates to a method of forming an encapsulationstructure for a multicolor organic electroluminescent display, and moreparticularly to a method of forming an encapsulation structure for anorganic light-emitting device (OLED).

BACKGROUND OF THE INVENTION

[0002] With the rapid developments of digital technologies, paneldisplays have become essential components for many electrical appliancessuch as notebooks, mobile phones, information appliances (IA) andpersonal digital assistants (PDA). Generally speaking, lightness,thinness and/or low electricity consumption are basic requirements oftypical panel displays. However, depending on viewing angles,brightness, high image quality and stability on temperature, relatedarts are required to be further developed. An organic light-emittingdevice (OLED) has been developed as a new technology for the nextgeneration of panel displays due to its properties ofself-light-emitting (without using a backlight), wider viewing angle,rapid response, simple manufacturing process and low energy consumption.

[0003] It is only quite recently to develop the technologies of theorganic light-emitting device (OLED) so that the related technologies ofthe organic light-emitting device (OLED) still have some problems to besolved. In particular, the moisture and the oxygen in the atmospherealways cause the cathode of the organic light-emitting device to beoxidized and the interface of the organic compound of the organiclight-emitting device to peel off easily. Such phenomenon may cause theorganic electroluminescent display to form dark spots, reduce the yieldand luminance of the organic electroluminescent display, and shorten theuse life of the organic electroluminescent display. In order to preventthe above-mentioned problems from happening, the traditional technologyemploys a metal-sealing container or glass-sealing container to seal andprotect the organic light-emitting device so as to avoid the materialsof the electrode layer and the organic layer contacting with theexternal environment.

[0004] However, the metal-sealing container is heavy and has theshortcomings of being oxidized easily during the manufacturing process,and the glass-sealing container is brittle, heavy and not easy toprocess. On the other hand, both the metal and glass materials are hardto adhere to the organic light-emitting device and the adhesive area ofthe organic light-emitting device isn't smooth enough. Therefore, theencapsulation structure of the organic light-emitting device is subjectto peel off. Moreover, there is a tendency to replace the glass materialof the substrate with plastic material so that the metal-sealingcontainer and glass-sealing container will be discarded in the future.In order to promote the organic light-emitting device to be lighter andthinner, and fit in with the tendency of entirely plasticizing theorganic light-emitting device in the future, the compact encapsulationand protection structure produced by means of plating should bepositively strengthened and further researched.

[0005] Please refer to FIG. 1, which shows a cross-section view of anencapsulation structure for a conventional organic light-emittingdevice. As shown in FIG. 1, the organic light-emitting device 10generally includes a substrate 101, a first conductive layer 102, anorganic light-emitting multilayer structure 103 and a second conductivelayer 104. The substrate 101 is a glass substrate or a metal substrate,and the first conductive layer 102 is an indium tin oxide (ITO) film oran indium zinc oxide (IZO) film. The second conductive layer 104 is oneselected from a group consisting of a metal film, a metal compound film,an indium tin oxide (ITO) film and an indium zinc oxide (IZO) film. Inorder to avoid the electrode layer and the organic layer of the organiclight-emitting device contacting with the external environment, thereshould be an encapsulation or protection structure 11 formed on theorganic light-emitting device 10. The traditional and essentialencapsulating steps for the organic light-emitting device 10 aredescribed as the following.

[0006] First, the polymer material, such as the polymer precursor ofmethacrylate, is plated on the organic light-emitting device 10 via athermo-sublimation method. The polymer material is polymerized to formthe first buffer layer 111 by means of light illumination. Then, aninorganic or a ceramic material is employed to form the firstpassivation layer 112 on the first buffer layer 111 by means ofsputtering or chemical vapor deposition (CVD) in the reaction chamber.Thereafter, the substrate 101 is delivered to the polymer-depositionchamber to form the second buffer layer 113 on the first passivationlayer 112. Finally, the entire substrate 101 is delivered to thereaction chamber of the inorganic or ceramic material for forming thesecond passivation layer 114 on the second buffer layer 113. Thematerial layers of the encapsulation structure 11 could be produced bymeans of repeating the above-mentioned steps according to therequirements.

[0007] During the process of forming the encapsulation structure 11, theentire substrate 101 must be delivered repeatedly between thepolymer-deposition reaction chamber and the thermo-sublimation chamberfor forming the buffer layers and the passivation layers respectively.Such repeating process is complex. Furthermore, it is also important toconsider whether the light would influence the organic material of thedevice when the organic light-emitting device is a top emission typeorganic light-emitting device.

[0008] Therefore, it is desired to provide an encapsulation structurefor an organic light-emitting device, which is capable of being producedeasily, efficiently and at low cost, and can rectify those drawbacks ofthe prior art and solve the above-encountered problems.

SUMMARY OF THE INVENTION

[0009] It is therefore an object of the present invention to provide amethod of forming an encapsulation structure for an organiclight-emitting device, which is performed in a single chamber andcapable of being applied to the organic light-emitting device with glasssubstrates, metal substrates and plastic substrates. Thereby, theencapsulation structure of the organic light-emitting device is lighter,thinner and fine-confluence, and the use life of the organiclight-emitting device is increased.

[0010] To achieve the above-mentioned objects of the present invention,a method of forming an encapsulation structure for an organiclight-emitting device is provided. The method includes steps of placingan organic light-emitting device into a plasma chamber, forming a firstbuffer layer on the organic light-emitting device by means of PECVDwithout exposing the polymer precursor to be solidified, forming a firstpassivation layer on the first buffer layer, forming a second bufferlayer on the first passivation layer, and forming a second passivationlayer on the second buffer layer, wherein the first buffer layer, thefirst passivation layer, the second buffer layer and the secondpassivation layer are formed via a process of plasma polymerizationperformed in a single plasma reaction chamber.

[0011] In an embodiment, the plasma polymerization process can be aprocess of plasma enhanced chemical vapor deposition (PECVD),high-density plasma chemical vapor deposition (HDPCVD) or inductivelycoupled plasma chemical vapor deposition (ICPCVD). In addition, themethod further includes a step of surface treatment or a step ofself-clean with the organic light-emitting device for demand whileforming the buffer layers and the passivation layers. Preferably, thefirst passivation layer and the second passivation layer are made ofdiamond-like carbon materials. More preferably, the first buffer layerand the second buffer layer are formed by a polymer film made of apolymer precursor, which is one selected from a group consisting ofstyrene, acetylene, ethylene, methylbenzene and octafluorocyclobutane(C₄F₈).

[0012] In accordance with one aspect of the present invention, theorganic light-emitting device could be a passive matrix organiclight-emitting device or an active matrix organic light-emitting devicecapable of emitting light downwardly or upwardly. Preferably, thesubstrate is a glass substrate or a plastic substrate.

[0013] In accordance with another aspect of the present invention, theorganic light-emitting device includes a substrate, a first conductivelayer formed on the substrate, an organic light-emitting multilayerstructure formed on the first conductive layer, and a second conductivelayer formed on the organic light-emitting multilayer structure.

[0014] The above objects and advantages of the present invention willbecome more readily apparent to those ordinarily skilled in the artafter reviewing the following detailed description and accompanyingdrawings, in which:

BRIEF DESCRIPTION OF THE DRAWINGS

[0015]FIG. 1 shows a cross-section view of an encapsulation structurefor a conventional organic light-emitting device; and

[0016] FIGS. 2(a)-2(d) are the cross-sectional views showing the flowprocess of forming an encapsulation structure for an organiclight-emitting device according to a preferred embodiment of the presentinvention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

[0017] The present invention discloses a method of forming anencapsulation structure for an organic light-emitting device. Theorganic light-emitting device is roughly divided into passive matrixtype and the active matrix type. For describing the main technology ofthe present invention clearly, a passive matrix organic light-emittingdevice is introduced as an embodiment in the following descriptions. Itis to be noted that the present invention needn't be limited to thepassive matrix organic light-emitting device. On the contrary, otherkinds of organic light-emitting devices, such as an active matrixorganic light-emitting device capable of emitting light upwardly ordownwardly, are also cooperated herewith for reference. In addition, thesubstrate of the organic light-emitting device needn't to be limited toglass substrate. The metal substrate and the plastic substrate are alsocooperated herewith for reference.

[0018] Please refer to FIGS. 2(a)-2(d), which are the cross-sectionalviews showing the flow process of forming an encapsulation structure foran organic light-emitting device according to a preferred embodiment ofthe present invention. As shown in FIG. 2(a), firstly, a passive matrixorganic light-emitting device 20 with a substrate 201, a firstconductive layer 202, an organic light-emitting device 203 and a secondconductive layer 204 is placed in a plasma chamber (not shown), and afirst buffer layer 211 is formed on the organic light-emitting device20. In FIG. 2(b), a passivation layer 212 is formed on the first bufferlayer 211 by means of plasma polymerization process. Then, as shown inFIG. 2(c), a second buffer 213 is formed on the first passivation layer212 via plasma polymerization process performed in the same plasmareaction chamber. Thereafter, as shown in FIG. 2(d), a secondpassivation layer 214 is formed via plasma polymerization processperformed in the same plasma reaction chamber. The steps of formingbuffer layers and passivation layers can be repeated according to therequirements. If a pattern is required, a shadow mask can be employed tocover the portion free from plating. Accordingly, the entireencapsulation structure is completed.

[0019] During the process of forming the encapsulation structure 21 forthe organic light-emitting device, the plasma polymerization process isplasma enhanced chemical vapor deposition (PECVD) performed with areaction gas containing methane (CH₄), methylbenzene (C₆H₅CH₃) oroctafluorocyclobutane (C₄F₈). In the plasma reaction chamber, both thefirst passivation layer 212 and the second passivation layer 214 aremade of diamond-like carbon material. Moreover, some metal materials,such as titanium (Ti), niobium (Nb), tantalum (Ta), chromium (Cr),molybdenum (Mo), tungsten (W), ruthenium (Ru), iron (Fe), cobalt (Co),nickel (Ni), aluminum (Al), copper (Cu), gold (Au), or silver (Ag) orsome nonmetal materials, for example silicon (Si) or III-V groupelements, can be selectively doped for adjusting the parameters of theprocess according to the requirements. In addition to the plasmaenhanced chemical vapor deposition (PECVD) process, high-density plasmachemical vapor deposition (HDPCVD) process, inductively coupled plasmachemical vapor deposition (ICPCVD) or other plasma polymerizationprocess can also be applied in the present invention. Furthermore, thefirst buffer layer 211 and the second buffer layer 213 are formed in thesame reaction chamber performed with a reaction gas containing a polymerprecursor. The polymer precursor can be selected from a group consistingof styrene, acetylene, ethylene, methylbenzene and octafluorocyclobutane(C₄F₈), and will form a polymer film of a polymer precursor, such as apolymer diamond-like carbon film, so as to form the first buffer layer211, the second buffer layer 213, the first passivation layer 212 andthe second passivation layer 214 in a signal plasma reaction chamber.Certainly, an additional buffer layer (not shown) can be further formedon the second passivation layer 214, if necessary. After that, anadditional passivation layer (not shown) can also be formed to preventthe organic light-emitting device from contacting the externalenvironment.

[0020] The present invention employs the plasma polymerization processto sequentially form the first conductive layer 211, the firstpassivation layer 212, the second buffer layer 213 and the secondpassivation layer 214 on the organic light-emitting device 20 in asingle plasma reaction chamber. So the drawbacks of forming theencapsulation structure by means of delivering the organiclight-emitting device among different reaction chambers will be solved.For increasing the surface cleanliness and smooth level of theencapsulation structure, a step of self-clean and surface treatment withthe organic light-emitting device could be introduced in the reactionchamber before performing the plasma polymerization process. Thereby,the surface cleanliness of the encapsulation structure is ensured.

[0021] Because the encapsulation structure 21 is used to completelyisolate the organic layer and the conductive layer of the organiclight-emitting device 20 from the external environment and toeffectively dissipate the heat produced by the organic light-emittingdevice operated over a long period of time, the materials with highconfluence and good thermal conductivity are the best choice for theencapsulation structure. Comparing the diamond-like carbon (DLC)materials of the present invention with the traditional organicmaterials or ceramic materials, the DLC materials are excellent inanti-friction and thermally conductive, and simultaneously has a featureof low water penetration. In addition, the DLC materials could form apolymer DLC film with low hardness or an amorphous DLC film with highhardness according to the manufacturing methods, the doped materials andthe parameters of the manufacturing process. Moreover, the color of theDLC film could be adjusted from brown to transparent. Hence, theencapsulation structure formed by the DLC materials can effectivelyprevent the organic light-emitting device from contacting with theexternal environment. Additionally, the second passivation layer 214covering around the entire encapsulation structure will increase thewear-resistance of the organic light-emitting device and the use life ofthe organic light-emitting device.

[0022] In conclusion, the present invention provides a method of formingan encapsulation structure for an organic light-emitting device. Themethod of the present invention employs the plasma polymerizationprocess and the diamond-like carbon materials to form the passivationlayers, and introduces the plasma polymerization process and the polymerprecursor to form the buffer layers, thereby forming the encapsulationstructure in single plasma reaction chamber. The buffer layers are usedfor absorbing the stress formed between the first passivation layer andthe second passivation layer. The method of the present invention cansolve the drawbacks of the prior encapsulation structure formed by meansof delivering the organic light-emitting device among different reactionchambers, simplifies the manufacturing process, decrease themanufacturing cost, and effectively prevent the organic light-emittingdevice from contacting the external environment.

[0023] Furthermore, the encapsulation structure with the diamond-likecarbon materials is highly compact, excellent at thermal conductancewear-resisting, high hardness and corrosion-resisting so as to fit inwith the demand of the organic light-emitting device. Accordingly, thepresent invention possesses many outstanding characteristics,effectively improves upon the drawbacks associated with the prior art inpractice and application, produces practical and reliable products,bears novelty, and adds to economical utility value. Therefore, thepresent invention exhibits a great industrial value.

[0024] While the invention has been described in terms of what ispresently considered to be the most practical and preferred embodiments,it is to be understood that the invention need not be limited to thedisclosed embodiment. On the contrary, it is intended to cover variousmodifications and similar arrangements included within the spirit andscope of the appended claims, which are to be accorded with the broadestinterpretation so as to encompass all such modifications and similarstructures.

1. A method of forming an encapsulation structure for an organiclight-emitting device, comprising the steps of: placing said organiclight-emitting device into a single plasma chamber; forming a firstbuffer layer directly on said organic light-emitting device; forming afirst passivation layer on said first buffer layer; forming a secondbuffer layer on said first passivation layer; and forming a secondpassivation layer on said second buffer layer, wherein said first bufferlayer said first passivation layer said second buffer layer and saidsecond passivation layer are formed in said single plasma chamber. 2.The method according to claim 1 wherein said first buffer layer, saidfirst passivation layer, said second buffer layer, and said secondpassivation layer are formed in an adjustable and repeatable sequence.3. The method according to claim 1 wherein said first buffer layer, saidfirst passivation layer, said second buffer layer and said secondpassivation layer are formed via a plasma polymerization process.
 4. Themethod according to claim 3 wherein said plasma polymerization processis plasma enhanced chemical vapor deposition (PECVD) process.
 5. Themethod according to claim 3 wherein said plasma polymerization processis a high-density plasma chemical vapor deposition (HDPCVD) process. 6.The method according to claim 3 wherein said plasma polymerizationprocess is inductively coupled plasma chemical vapor deposition (ICPCVD)process.
 7. The method according to claim 1 further comprising a step ofsurface treatment with said organic light-emitting device.
 8. The methodaccording to claim 1 further comprising a step of self-cleaning withsaid organic light-emitting device.
 9. The method according to claim 1wherein said first passivation layer and said second passivation layerare made of diamond-like carbon materials.
 10. The method according toclaim 1 wherein said first buffer layer and said second buffer layer areformed by a polymer film made of a polymer precursor.
 11. The methodaccording to claim 10 wherein said polymer precursor is one selectedfrom a group consisting of styrene, acetylene, ethylene, methylbenzeneand octafluorocyclobutane (C₄H₈).
 12. The method according to claim 1wherein said organic light-emitting device is a passive matrix organiclight-emitting device.
 13. The method according to claim 1 wherein saidorganic light-emitting device is an active matrix organic light-emittingdevice.
 14. The method according to claim 13 wherein said active matrixorganic light-emitting device emits light downwardly.
 15. The methodaccording to claim 13 wherein said active matrix organic light-emittingdevice emits light upwardly.
 16. The method according to claim 1 whereinsaid organic light-emitting device comprises: a substrate; a firstconductive layer formed on said substrate; an organic light-emittingmultilayer structure formed on said first conductive layer; and a secondconductive layer formed on said organic light-emitting multilayerstructure.
 17. The method according to claim 16 wherein said substrateis a glass substrate.
 18. The method according to claim 16 wherein saidsubstrate is a plastic substrate.